The present invention relates to a heating, venting, and/or air conditioning unit for vehicles, especially a unit arranged at the roof of a cabin vehicle, having at least one blower and air channels which are connected to the suction side (suction channels) and/or pressure side (air distributing channels) of the blower.
Such heating, venting, and/or air conditioning units are, for example, known from German Offenlegungsschrift 28 41 277. It is a well-known problem of cabin roof heaters that while space is saved within the floor space of the usually cramped cabin and unused free space at the roof of the cabin is used instead, the vehicle is, however, made top-heavy and the roof construction must be reinforced resulting in constructive disadvantages.
A special problem with the use of so-called double radii blowers for a roof heater is that special measures must be taken in order to prevent resonances within the support structure of the blower. Resonance oscillations result in considerable loads on the fastening elements, have negative effects on the long term service life, and increase considerably the noise development resulting from the roof heater. In order to prevent resonances with roof heaters a conventional measure in the past has been to eliminate large volume pressure distributing chambers even when enough space is available at the roof and to provide support plates of a considerable thickness.
However, the lack of a pressure distributing chamber downstream of the blower results in non-uniform flow conditions and requires special measures especially in order to supply air, in addition to the air supplied to the windshield, to other windows especially the rear window, in order to defrost it. A pressure nozzle which makes a pressure distributing chamber downstream of the blower obsolete is suggested in German Offenlegungsschrift 28 41 277.
It is an object of the present invention to provide a heating, venting, and/or air conditioning unit of the aforementioned kind which despite a comparatively small weight of the support structure allows for a resonance-free support of the blower whereby at the same time a cost-effective manufacture should be possible.